Multiple strand thermal pull wire unit



May 19, 1953 P SITZER 2,639,190

MULTIPLE STRAND THERMAL PULL wI'RE UNIT Original Filed Jan. 20, 1945 2 Sheets-Sheet 1 INVENTOR. PH/z/P 5/7752 'BY H/S ATTORNEYS P. SITZER MULTIPLE STRAND THERMAL PULL .W IRE UNZ ET Original Filed Jan. 20, 1945 May 19, 1953 2 Sheets- Sheet 2 IN VEN TOR. PH/z/P S/rzm BY HIS A T T OENE Y6 M M M Patented May 19, 1953 MULTIPLE STRANQHEHERMAL PULL WIRE Philip Sitzer, Irvington, N. J assignor to Tung- Sol Electric Inc., Newark, N. J., a corporation of Delaware Continuation of application Serial No. 573,736, January 20, 1945. This application September 19, 1949, Serial No. 116,597

1 Claim.

This invention relates to vane type thermal switches of the type controlled by the expansion and contraction of a pull wire element.

One object of the invention is a new and improved vane type thermal switch characterized by its dependability, uniformity of operating characteristics over long periods of time, and the uniformity of operating characteristics of the devices when produced in quantity.

Another object of the invention is a new and improved vane type switch of the above character wherein a large uniform operating force is applied to the vane and wherein uniform operating characteristics over long periods of time and uniformity of operating characteristics of switches produced in quantity are obtained.

Another object of the invention is a new and improved vane type thermal switch characterized by its simplicity of structure.

Still another object is a new improved vane type thermal switch.

For a better understanding of the invention reference may be had to the accompanying drawings, of which-- Fig. 1 is a side view of the multiple pull wire of a thermal switch embodying the invention;

Fig. 2 is a view taken at right angles to Fig. 1 and as viewed from the left;

Fig. 3 is a fragmentary view on an enlarged scale showing the supporting means for the multiple pull wire of the switch of Fig. 1;

Fig. 4 is a perspective view of the thermal switch of Figs. 1 and 2 mounted in an envelope;

Fig. 5 is a side view of another embodiment of the invention;

Fig. 6 is a view thereof at right angles to Fig.

Fig. 7 is a perspective view of this embodiment housed in a casing;

Fig. 8 is a view illustrating one step in the method of forming and mounting the multiple strand wire unit of the embodiment of Figs. 5 to 7 Fig. 9 illustrates another step;

Fig. 10 illustrates another step;

Fig. 10a is a sectional view through the assembly of Fig. 10;

Fig. 11 illustrates another step in the method;

Fig. 12 illustrates a further step in the method;

Fig. 13 is a view of a detail of the multiple strand unit of Figs. 5 to 7; and

Fig. 14 is a perspective view of a detail of the mount of Figs. 5 to '7.

In Figs. 1 to 4 I have illustrated one embodiment of my new and improved switch structure having in combination a snap action vane type switch actuator and a multi-strand thermal pull wire wherein the stress on each strand is equalized to provide more dependable positive operation and more uniform characteristics throughout its life. More particularly the switch comprises a sprung vane 2 secured at its ends to a frame memher 4 and carrying a contact 6, a fixed contact 8 engageable by the contact 6 in one position of the vane 2 and a coil I0 of expansbile wire, the contraction and expansion of which control movement of the vane to and from contact closing position.

In accordance with this embodiment of the invention the coil I0 is supported at its ends by members [2 of insulating material about which the wire is wound under tension so as to provide a plurality of strands extending between the members with the strands being uniformly tensioned at all times. In the particular embodiment shown these members [2 are tubular in shape. The members I2 are mounted on bars or rods M which pass therethrough. The ends of these rods are secured to the arms of V or U-shaped yoke members IS. The upper yoke member [6 hangs on one arm of a right angle bracket [8, the other arm of which is secured to the vane 2, the bracket being provided with a U-shaped section 20 for reception of the yoke member. The central stretch of the lower yoke member it passes under one arm of a bracket 22, the other arm of which is secured to one end of vane 2 where it is attached to the frame 4, the bracket 22 being provided with an inverted U- shaped section 23 for reception of the yoke memher.

With this structure I eliminate all mechanically operated levers and knife-edge pivots that restrict movement to one plane and thereby enable the several switch elements to cooperate to provide greatly improved operation and with uniform stress on the several strands.

The wire forming the coil I0 is preferably suitably insulated as by an enamel coating and the number of turns. and the diameter of the wire are such that the coil has a relatively high resistance. As one example, when enameled Nichrome wire of .0008" diameter is used to form the coil l0 and a sufficient number of turns provided, the power absorbed by the coil is less than milliwatts. The stretches of the coil [0 are preferably secured'to the members [2 by means of cement 24 as shown best in Fig. 3.

With the above described arrangement, the tension of the strands of coil 10, when the wire forming the same is cold, acting through the upper yoke member and bracket l8 holds the vane 2 in one constrained position. When electric current flows through the coil It the wire expands andpermitsthevane 2 tosnaptoanother position. Because of the particLrla-ryoke mounting of the coil, that is, because of the free suspension of the upper yoke member from the bracket l8 and similar coupling between the lower yoke member and bracket 2-2,la ny-unequal pull of a wire or wires on one end of a spool l2 tends to shift the yoke or yokes about thesuspension points so as to equalize thegpull ofrall'ithewires. Thus there will be a balanced distribution of the tension among the various strands of the coil, with resultant improved operation oftl-ie s'witch.

As shown in Fig. 4, the fram'e l' may be'm-ounted on an insulating disk 26 of glass or the like,

forming a closure for a glass vessel 28 enclosing the switch elements. Electrical terminals so on theunder side of thedisk, suitably connectedwith the endsof the coil-iii, withtheiixed .con-tact fl --andwith thefframe ll,. pro'vide. means for connecting 1 the thermal switch into the circuit it I is to comm.

h The frame 4 is lmounted on support .wirestz one of. whichserves as the electrical connec-tiontoone terminal .30. The fixed contact 8 iscarried on the end of awireit l which is insu- JatedIyYmOunted on the lirame by meansofa bea'dlilfi fused about the wire and secured tola :strip 38 carried-by the'lfra'me, the other end of the.wirefiiil'.beingconncted to. a terminalte.

In the embodiment of'Figs. 5, '6 andfllthe mu1- tiplestrandpull wireisforlnecl. of a unitl th with the; ends or'turns oflthemultiplewire coils firmly by welding to the vane '2. lhe eyeletf l3lisformed aroundits edge with aicurved seatfii .for the reception of thebead il. The eIid ofthe bracket arm 44 i slprovi'ded with a slot 'tfiextndirigirom ftheleyelet t3 outward, which'fperrnitls assembly of '.'the bead within-the e'yelet ii' by pas's'ir'igthe multiple'strand wire'through this .slot .45. The

innit is mounted in'abracket 38 which is lidntical Wvith'the bracket 1% in which lthe bea'd ltis mountedbutin this .case the'iiange" 86'-.of the "bracket 136' is'fastened as by welding to theifraine t. "The switch shown. in IFigsj Sand 6 may .be

mounted in an envelope indicated at lifi'having four terminals lf llif lll and es withthe terminals ll and 33 leading to the multiple :stranol unit as. The terminal ltlea dsto theiiame i and the terminal 5!) leads to the supports -for the'fixed contact .8. "In the. particular embodiment shown 'inFig. lithe contact-actuating arm 8"is"ins'ulate'dly carried by a LI -bracket 5l fastened to the frame i"with a connecting wire 52l'lea'd'i'ng from the contact carr'ierltto' the leadin .wire 50. .YAlso in the 'particfilaneir'ibodimtaht shown,'. the frame l iscarricd by 'apa'ir-offisupport WiresYlsBerribeddd in the'end of'the .en-

velope, one of these wires -.53 leading to=the terminal '49.

The multiple strand .pull wire maybe coiled and-inounted in the beads t! and thin any-suit- "abler-mannerabut inF-igs. 8 to 12.1 have illustrated a new and improved methodlfor accomplishing this-purpose. The first step (Fig. 8):con-

'sists in-coi-li-ng the wire i'6t --about-apairofspaced i To very small diameter mandrels (ii with the turns Ell of the wire evenly placed and adjacent each other. Preferably the wire es is provided with an enamel or other insulating coating so that 5 even thoughthey may touch they are insulated eagainst short circuit by this insulation from the comparatively small voltage difference between .the turns. With the wire 65; thus wound tightly about the spaced mandrels 6! the multiple estr-an'ds arelforrned.in co-p1anar layers E2 spaced from each other a distance equal to the diameter of the mandrels tl (Fig. 8(a) and (b) The next istepiinthe formation oi the unit is shown in"Fi'g. .19. 'ihis step consists in gathering the main body of the multiple wires 52 rather closely together and then embedding or enoasing the =-gatlieredtogether-multiple Wires or turns St in "wax or anyother readily removable material foratemporarily holding the multiple strand wire in assembled relation while mounting. This readily removable enc'asing material in which the multiple? strand i fire is embedded is indicated attS 'a'n'd'it preferably eitends to point not very far removed from the mandrellii (at both ends "so as "to leave uncasedparts "1612" at the ends of the multiple -strzmol assenibly. "Thus the multiple strand assembly'isheld firmly in the assembly unit with the strands oi"wiie parallel to each other and closelygrou'pe'd whereby the pull of the group approaches that or a single pull wire. "fig. '9 roughly illustrates "the "close grouping of the wirestfl inthe temporarycasing "lheimandrels iii are removed, lea'vingthe assenib en unit as illustrated in'Fis. l0. "The next step is illustrate d'in "llan'd" this cons'ists'in'assembling over the ends"ftl2"ofthe coiled multiple strand wire hollow .'glass beads iifi whichare' in the form For cups as shown 'in'detail in "Fig. '13, each with a small'hole 5'6 formed in the bottom or the cu the open top of the cup being shown attl. The exposed entlsl'ii" multiple wire strand assembly "are inserted throughthese small openings ."66 with the'open sidesofthe cup-ishapedbeads i535 disposed outwardly of .the assembly, the ends'ofthe multiple' strand coil assemblies "ee'iteri'clin'g through the ends ofitheicup-shaped' headset" to a point where 'the' end surfaces ofthe 'coihturns are: approximately or nearly approximately even with the 'operrsi deprends 'of thebeads. These Deserts arepreierablyhf glass 'bu'ttl'iey inay'be of any other suitable material. lhe'ne'zit stepfconsists -in-anclrioring the'ends f'the"mll1l7l "e strand coil assembly to' the hollow "glass beads $5. step is illustrated in Mg. '12 consists in filling each or the hollow beads iitwith a suitable-cemented, care'beine taken that each end of the coil is covered with and embedded inithe cement. The "cement may beanysuitable' cement which upon hardening firmly "the ends "62of theniultiple-strand-assembly to theelass beads. This cement is erab'ly of insulating material. 'Afterthe cement hasbeen properly dried the wax casing 63 in which tlleinain' body of the wire assemblyis-"ein'be'd'de'dnan 'thenibe dissolved or melted 'ol'Pso-"as todea've the 'm'ultiple strand closely assembled "wire'st ands'fl exposed all the way between the glass beads "65. Fig. 'sh'o-ws the wa casing thus removed and 'the structure at the ends I are indicated at il and 52. l/ls -above describe'd the unit thus formed may be placed *i n-the'fiasherpr relay -which .i'ha's' suitable eyelet supports. As shown in Figs. 5, 6 and '7 illustrating a thermal switch of the sprung van type the rounded surfaces :65 eof the beads resti upon it'he sea-ts i3 roamed around the eyelets. The beads 65 may also be formed of an insulating material and molded in place about the ends 62' of the wires 92.

A thermal switch is thus obtained having multiple pull coils of fine wire which simulates very closely a single pull wire, with all strands of the parallel turns of wire assembled closely adjacent a central point. The creation of uneven pull among the individual wires when the unit is adjusted or when it is operating is thus largely obviated and for practical purposes the pull is substantially uniform on all strands of the wire. As above indicated the relay may be used in either hot wire flashers or relays.

No particular circuit has been illustrated in the drawings as circuits suitable for control by thermal switches of the general type herein described are well known and form no part of the present invention.

From the above description it will be apparent that the invention provides an improved mount for the multiple wire coil of a thermal switch that insures uniform balanced pull of the various strands of the coil.

In both the modification of Figs. 1 to 4 and the modification of Figs. 5 to 14 the pull of the multiple strands collectively and individually is exerted substantially at a common point, in the first modification at the hooks 29 and 23 of the brackets l8 and '22 and in the second modification at the eyelet 43, with the members it and 44 functioning as the means for transmitting the pull of the multiple wire unit directly to the movable contact and with the small mandrel l2 and yoke mount and the beads 4|, 42 being directly attached to the multiple wire assembly for transmitting the pull to the members I8 and 44.

Particularly good results have been obtained with my new and improved multi-strand structures in combination with the vane type switch illustrated in the drawings as they cooperate to insure precise, positive and dependable switch operation throughout the switch life. Moreover, with this new and improved structure I have eliminated all mechanical levers and knifeedg'e pivots and use in effect as the only moving part a buckling vane which together with the improved multi-strand structure provides in addition to a simple, dependable unit one that can be readily produced in quantity at low cost.

Furthermore, my improved pull wire mounting and method also effects further reduction in manufacturing costs and enables substantially uniform stress to be placed on each end.

This is a continuation of my application Serial No. 573,736, filed January 20, 1945, now abandoned.

I claim:

A multiple pull wire unit for mounting in a thermal switch comprising multiple turns of fine Wire closely disposed to each other with the opposite ends of the multiple strand unit disposed in insulating cup-like shells having a hemispherical bottom part including a central opening therein, with the wires passing through said opening and a cement-like filler in the shell in which the ends of the wires are embedded.

PHILIP SITZER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,237,470 Carrier Aug. 21, 1917 1,991,059 Norwood Feb. 12, 1935 2,133,399 Schmidinger Oct. 18, 1938 2,198,131 Shaw Apr. 23, 1940 2,256,499 Schmidinger Sept. 23, 1941 2,326,239 MacL-aren, Jr Aug. 10, 1943 2,344,530 Askew Mar. 21, 1944 2,388,712 Schmidinger Nov. 13, 1945 2,389,517 Labadie Nov. 20, 1945 2,457,094 Smith Dec. 21, 1948 

